(a) Technical Field
The present invention relates to a device and a method for controlling a battery State of Charge (SOC) of a hybrid vehicle, more particularly, to a device and a method for controlling a battery SOC in accordance with gradient information of a road ahead using the gradient information of the road ahead and a feedback from a driver.
(b) Description of the Related Art
As is widely known, when a navigation system for a vehicle including gradient (altitude) information is used to set a destination, information (i.e., information such as a gradient, a speed limit, traffic information, etc.) on a route from a current location to the destination may be provided.
In the case of a hybrid vehicle, effects on fuel efficiency by an energy management strategy including power distribution between an engine and a motor, engine on/off, management of a battery State of Charge (hereinafter, abbreviated as “SOC”) are significant so that when predictive energy management is performed using information on a road ahead from the navigation system, the effect on fuel efficiency of the hybrid vehicle may be maximized.
When a driver knows a driving route to a destination, the driver frequently drives the vehicle without setting the destination using the navigation; however, when the route is not set, the predictive energy management using the front gradient information may not be appropriately performed.
For example, after charging or discharging the battery SOC, because a downhill/uphill route ahead on the road on which the vehicle is currently running is recognized, when the driver changes a driving route which is not the downhill/uphill route or even when the predictive energy management control is performed in consideration of the uphill which is followed by the downhill, the destination of the driver is after the uphill and before the downhill, the predictive energy management control is erroneously predicted without recognizing the driving intention of the driver, which may adversely affect fuel efficiency.
Among the predictive energy management control items, a battery state of charge (SOC) control strategy manages the energy by a post-response manner without considering information on the road ahead.
The post-response manner refers to a manner in which when the battery SOC is out of a predetermined range in accordance with road, traffic, and driving conditions, compensation therefor is performed.
For example, according to the post-response manner, as illustrated in FIG. 4 (RELATED ART), when the battery SOC exceeds a set normal band (for example, 45 to 60%), a discharging-oriented strategy is selected to increase the usage of electric energy, but when the battery SOC is lowered to a low band which is below the normal band, a charging-oriented strategy is selected to increase a torque of an engine for charging the battery to return the battery SOC to the normal band.
However, when the battery SOC is lowered to the low band and a high power driving circumstance occurs in accordance with an environmental change (for example, a gradient of the road ahead during driving), there may not be sufficient power to charge the battery due to insufficient power of the engine, and the engine operates at an inefficient driving point due to restricted electric energy usage, which may deteriorate the energy efficiency.
When the battery SOC reaches a high state without recognizing a long downhill road condition ahead, the energy which may be obtained by a regenerative braking system may be wasted due to an early fully charged battery.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.